/Engine/Source/Developer/TargetPlatform/Public/Interfaces/IAudioFormat.h
This is called prior toSplitDataForStreaming(), and is used for determining FirstChunkMaxSize.
virtual int32 GetMinimumSizeForInitialChunk ( [FName](API\Runtime\Core\UObject\FName) Format, const [TArray](API\Runtime\Core\Containers\TArray)< uint8 > & SrcBuffer ) const